It is known that amphiphilic molecules may be caused to aggregate in solution to form two or three dimensional ordered arrays such as monolayers, micelles, black lipid membranes, and vesicles or lisosomes, which vesicles may have a single compartment or may be of the multilamellar type having a plurality of compartments.
The selectivity and flux of ions through membranes can depend on the number, size and detailed chemistry of the pores or channels that they possess. It is through these pores or channels that permeating solute molecules pass across the membrane.
It is known that membranes may incorporate a class of molecules, called ionophores, which facilitate the transport of ions across these membranes. Ion channels are a particular form of ionophore, which as the term implies are channels through which ions may pass through membranes. The measurement of current flow across membranes due to a single ion channel is known and typically yields a current of 4 pA per channel.
The use of membranes including ion channels in biosensors has been proposed. In co-pending International Patent Application No. W089/01159 (published 9 Feb. 1989) the production of biosensors incorporating membranes including ion channels is disclosed. The disclosure of this application is hereby incorporated by way of cross-reference. The present invention seeks to provide biosensors of greater sensitivity.